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94 Truck Drayage Productivity Guide input. Although gate transaction data might be obtained through a railroad representative, issues of accuracy, completeness, and interpretation may need to involve the contract operators. Container Depot Data Most container depots are privately operated, either by one of a few regional or national companies, or by local entrepreneurs. They store containers for ocean carriers and leasing companies. Depots also maintain and repair containers, but the activity model does not dis- tinguish trips for repair or maintenance from trips for storage. Container depots keep elec- tronic records of their transactions, but as private companies, their cooperation in providing data is strictly voluntary. Shipper and Receiver Data Obtaining reliable distance and volume information for shipper (export) and receiver (import) trips can be a considerable challenge. The actual locations and container volumes are known only to the shippers and consignees themselves, and perhaps to the drayage firms that serve them. Port marketing and sales departments can be a source of insight on the actual locations of port customers and for customer contact information. Street Turn and Crosstown Data Ordinarily, there is no organization that keeps data on street turns and crosstown trips, so esti- mates are required. Two factors are at stake: the frequency of street turns (reuse of import con- tainers for export loads) and other crosstown trips, and the distance commonly traveled. In both instances, major drayage firms would be the best sources for estimates. National Drayage Cost and Emissions Estimates In NCFRP Project 14, the study team used the EPA SmartWay DrayFLEET Model to estimate vehicle activity associated with port drayage, its cost, and resulting emissions. In 2008, U.S. ports handled a total of 22,597,601 TEU in about 13 million individual containers. The DrayFLEET Model was used to estimate the operational, financial, and environmental costs of container drayage at the nation's ports. The DrayFLEET Model was configured with a weighted average drayage distance of 5 miles and no waiting time at customer locations. These modifications effectively restrict the model to a 5-mile working range around the port terminals. This step was necessary to focus the analysis on differences in terminal and port-area operations rather than to have the potential improve- ments observed by over-the-road operations. The 13 million containers required an estimated 41.6 million drayage trip legs, an average of 3.2 per container. Those trips required an estimated 39.1 million driver and tractor hours to cover 326 million miles. The model estimates that 45% of the drayage hours in the vicinity of the ports were spent idling, which is generally consistent with most driver survey results. About 26% of the hours were spent in "creep" mode, essentially low-speed, stop-and-go operation typical of queuing or in- terminal operation. This allocation highlights the amount of time--nearly 18 million hours annually--that drayage drivers and their tractors spend idling. In those operating hours, port drayage tractors burned an estimated 69.9 million gallons of diesel fuel and emitted 782,613 tons of CO2, the major greenhouse gas impact (see Table 122).